The present invention relates to a silver halide photographic material, more particularly, to a silver halide photographic material having improved sharpness and a high degree of whiteness.
Silver halide photographic materials are chiefly intended to record optical information, so it is one of the most important capabilities for them to provide faithful spatial reproduction of optical information.
Light incident upon the surface of a light-sensitive material will propagate through the material as it undergoes spatial spread on account of various factors. This spread of light can prevent faithful reproduction of optical information. Major causes of light spread are:
(1) scattering of light on the surface of a light-sensitive material, at the interface between photographic layers, or at the interface between a photographic layer and the support;
(2) scattering of light by silver halide grains in photographic layers, solid particles such as those of a matting agent, or by oil globules; and
(3) scattering in the support.
With a view to taking the full advantage of rapid processing, it has recently become popular to use paper base coated on both sides with polyolefins and other resins as supports for silver halide photographic materials. White pigments such as titanium dioxide are usually dispersed in the resin layer on the side of the support where an emulsion layer is coated. The pigment load in the resin is limited for several reasons such as dispersion stability and with titanium dioxide, about 15 wt % is normally the upper limit. However, the pigment load at this level is insufficient to prevent part of the incident light from passing through the resin layer and diffusing into the paper base. The light diffusing into the paper base will pass again through the resin layer to return to photographic layers where it exposes silver halide grains, thereby greatly impairing image sharpness due to blurring or diffusion.
In order to prevent light from diffusing in the paper base, it has been proposed that a hydrophilic colloidal layer containing a dye or colloidal silver be disposed between a photographic emulsion layer and the support to as to absorb the light that might pass through the photographic emulsion layer, thereby reducing the absolute amount of light that will reach the paper base. The hydrophilic colloidal layer disposed between a photographic emulsion layer and the support to attain this purpose is generally referred to as an anti-halation layer and is described in such references as Research Disclosure, vol. 175, Item 17559, November 1978, pp. 53-54 and ibid., vol. 187, Item 18716, November 1979, pp. 649-650.
In the case of photographic paper for photo type setting such as computerized photo type setting, the processed paper is often used as an original for process camera. If the surface of this paper has an unduly high gloss, image deterioration can occur on account of "flare". In order to prevent this problem, the surface of light-sensitive materials is usually given a mat finish. Two methods are known for attaining this purpose: one is to mat the surface of the support, and the other is to incorporate a matting agent in the topmost layer of the light-sensitive material. If the second method alone is used to reduce gloss, a considerable drop in photographic density will occur, so instead, a matted support is usually employed. In order to realize rapid processing, photographic paper for photo type setting also commonly employs a support composed of a paper base that is coated on both sides with resins such as polyolefins. For the purpose of preventing flare during shooting with a camera and to minimize possible decrease in photographic density, the degree of matting of the surface of the support for this type of photographic paper is usually adjusted to lie within the range of 0.3-1.5 .mu.m in terms of center-line-average roughness, Ra, as defined in JIS B 0601 as follows: